the modulatory role of orexin 1 receptor in ca1 on orofacial pain-induced learning and memory deficits in rats

Introduction: cognitive impairment is commonly associated with pain. the modulatory role of orexin 1 receptor (ox1r) in pain pathways as well as learning and memory processes is reported in several studies. the current study was designed to investigate the possible role of ca1-hippocampal ox1r on spatial learning and memory of rats following capsaicin-induced orofacial pain. methods: orofacial pain was induced by subcutaneous intra lip injection of capsaicin (100 μg). ca1 administration of orexin a and its selective antagonist (sb-334867-a) were performed 20 minutes prior to capsaicin injection. learning and spatial memory performances were assessed by morris water maze (mwm) task. results: capsaicin treated rats showed impairment in spatial learning and memory. in addition, pretreatment with orexin a (20 and 40 nm/rat) significantly attenuated learning and memory impairment in capsaicin-treated rats. conversely, blockage of ox1r via sb-334867-a (40 and 80 nm/rat) significantly exaggerated learning and memory loss in capsaicin-treated rats. conclusion: the obtained results indicated that ca1 ox1r may be involved in modulation of capsaicin –induced spatial learning and memory impairment.